Stereoscopic content may be distributed by broadcast television, stored on DVD's or other storage media, downloaded through the internet, transmitted by video phone, or distributed by other methods. In distributing stereoscopic content, it is desirable that the format of the stereoscopic content be compatible with many stereoscopic and non-stereoscopic display apparatus. It is also desirable that the amount of additional storage space or bandwidth required for stereoscopic content over non-stereoscopic content be minimal.
Stereoscopic images generally consist of two images which are related by a small change in the lateral perspective. When viewed through an enabling apparatus, stereoscopic images may provide the perception of stereoscopic depth. Stereoscopic content may be distributed as left and right image pairs or as anaglyph images. Stereoscopic content may also be distributed as a single image (stream) combined with a depth map (stream). The depth map may be used to generate a plurality of stereoscopic image pairs. Stereoscopic content may be compressed before distribution by methods similar to compressing non-stereoscopic content.
Anaglyphs are stereoscopic images wherein different sets of primary colors are used to render the first and second images of the stereo pair. Usually, the spectra of the first and second images do not overlap significantly. Then the first and second images may be viewed selectively using two complementary color viewing filters. The first viewing filter F1 may be used to view the first image while the second viewing filter F2 may be used to view the second image. The first filter substantially transmits the primary colors of the first image and blocks the primary colors of the second image. The second filter substantially transmits the primary colors of the second image and blocks the primary colors of the first image.
Anaglyphs are often rendered in three primary colors where the first image is rendered in two primary colors while the second image is rendered in one primary color. In red/cyan anaglyphs, the first image is rendered in green and blue primary colors while the second image is rendered in a red primary color. Other types of anaglyphs may include blue/yellow and green/magenta anaglyphs. Herein these anaglyphs are called three-color anaglyphs.
Distributing stereoscopic content as full-color left and right pairs may require substantial extra bandwidth or compression and de-compression processing that may inhibit the inclusion of stereoscope content in some of the distribution methods used for stereoscopic content. Distributing stereoscopic content in the anaglyph format using three primary color channels may require little extra bandwidth over non-stereoscopic content, however the anaglyph format is not sufficiently compatible with non-stereoscopic full-color display methods due to the lack of full-color information in the anaglyph format.
Some standard video formats such as the MPEG-C (Motion Picture Experts Group) format provide for an extra channel to accompany the video information. This extra channel may be used by methods in the prior art to provide a depth map video. The depth map video may be used to generate a plurality of stereoscopic views of the video content. These plurality of views may be used in autostereoscopic and other stereoscopic display methods to display stereoscopic images. Distributing stereoscopic content as a single image stream with a depth map stream allows stereoscopic information to be provided in a single channel and may be compatible with non-stereoscopic display methods. However a depth map generally does not provide for generating occluded data which occurs in one image of a stereoscopic pair of images, but not the other. The methods of including occluded data in addition to the depth map may reduce the compression ratio of the format and may require all stereoscopic displays to provide complex de-compression and image construction processing capabilities. Therefore, there is a need for alternate distribution methods which are highly compressible and compatible with many stereoscopic and non-stereoscopic display methods.